I have two identical 1X12s (SSP by Tracy), one has an E120 I know to be all original (I bought it in an NOS unopened original box), the other a K120 that I'd thought was all original but now I'm wondering.

There are two visible and performance differences in the speakers of note.

The first is the cone on the K120 is darker than the cone on the E120.

The second is the excursion on the K120 is greater than on any speaker I've owned. Not only is it quite easily visible even under moderate volumes, with the grill cloth cover on the amp, the flapping in and out of the grill cloth while playing through the speaker is readily noticeable. This is significantly less the case playing through the E120.

Not sure that can be the whole story - I have many other speakers in many other apps that I drive with equivalent wattage and none has the excursion of the K120 as far as I can tell - but it certainly may be part of it and I appreciate your reply.